Photographic color reproduction process



Apnl 2, 1957 A. MURRAY ET AL 2,787,543

PHOTOGRAPHIC COLOR REPRODUCTION PROCESS Filed Oct. 9, 1952 LIGHTSENSITIVE POLYMER COLOR SEPARATION NEGATIVE EXPOSURE AND SOLVENTDEVELOPMENT COLOR/N6 SUB TRACT/VELY YELLOW imam/m cm/v ALEXANDER. MURRAYEARL M. ROBERTSON INVENTOR.

ATT'Y a Aa'r 1 Claim. (CI. 96-14) This invention relates to a process incolor photography and more particularly to a color process involving thesuperimposition of colored polymeric relief images.

In the early stages of color photography, colored reproductions weremade by the subtractive method of color photography by superimposingsuitably colored gelatin relief images. It was early recognized that thevarious superimposed images should not undergo dimensional change in thepresence of heat and moisture and this led to the use of water-resistantsupports for the superimposed elements as well as for the transfer sheetupon which the superimpositions were made. As early as 1891,collodion-coated paper was used for this purpose and present-dayprocesses of this type still utilize sensitive tissues having acellulose derivative or other similar moistureresistant support. Glassand even wire screen have also been used to prevent the distortion ofthe images. In recent years in an effort to obtain films forsuperimposing which are more resistant to distortion in the presence ofmoisture, dichromate-sensitized colloid material such asdichromate-sensitized viscose and regenerated cellulose sheeting havebeen used. Obviously, such systems are relatively insensitive to lightaccording to modern standards, are still moisture-sensitive, and arerelatively unstable among other disadvantages.

In certain other well known processes of color photography in currentuse, the problem of distortion and registration of colored photographicimages has been met by superimposing the layers recording the separateaspects of a colored subject as in multilayer color films. However, incertain instances such as in the printing trade when it is desired toobtain proofs of colored printing plates, the superimposition ofindividually colored elements is still desired.

We have discovered that if there are employed for the formation ofsuitably subtractively colored relief images certain solvent-solublepolymeric materials having relatively high light-sensitivity and whichare relatively impermeable to moisture, the long-needed process yieldingmore dimensionally stable images for superimposition is made availableand some disadvantages of prior art methods are overcome.

One object of our invention is, therefore, to provide suitablelight-sensitive polymeric materials for use in making superimposedsubtractively colored relief images. Another object is to provide amethod for making the relatively dimensionally stable subtractivelycolored images for superimposition.

In the broadest phases of our invention we utilize a light-sensitivephotographic element having a support preferably transparent and havinghigh dimensional stability to some non-aqueous liquids, such as viscose,regenerated cellulose or a substantially fully esterified cellulose.ester such as cellulose triacetate and particularly surface-hydrolyzedcellulose acetate. This support is coated with a layer of an organicsolvent-soluble light-sensitive polymeric material having monomericunits containing groups of the structure wherein n is 2 or 3 and Rrepresents a mononuclear aromatic group of the benzene seriesor apolynuclear aromatic ted States Patent U. coupled withZ-smino-5-diethylamtuotoluene.

group as of the naphthalene series. A typical polymer is a cinnamic acidester of polyvinyl alcohol.

In the accompanying drawings are shown in greatly enlargedcross-sectional view in Figs. 1-4 the appearance of three representativesensitive elements at various stages in the process of our inventionwherein are prepared cyan, magenta and yellow colored relief images ontransparent supports which are superimposed to form a full coloredreproduction.

Our invention will now be described with particular reference to theaccompanying drawings.

EXAMPLE 1 As shown in Fig. 1 of the drawings, three sensitive elementsare provided having supports 10, 20 and 30, each carrying a layer oflight-sensitive polymeric material 11, 21 and 31. A support suitable forthis purpose is surface-hydrolyzed cellulose triacetate about .003 inchthick. Each of the three supports can be coated with a lightsensitivelayer from a composition such as the following:

Anisalacetylpolystyrene grams.. 6 Furfural .cc Tricresyl phosphate grams0.3

The polymer in the above composition is prepared as described in theUnruh et al. U. S. patent application Serial No. 246,516, filedSeptember 13, 1951, now U. S. Patent 2,716,097, Example 3 thereof, bythe condensation of anisaldehyde with polyvinyl acetophenone in thepresence of mineral acid.

After drying the coated elements, they are exposed through the baseseparately by contact with the usual continuous tone subtractive primarycolor separation negatives at 4 feet from a 35-ampere carbon are. Withthe particular set of negatives used, the magenta negative required 10seconds exposure, the cyan 7 seconds and the yellow 12 seconds, theexposure difference being due primarily to differences in maximumdensity of the separation negatives. The result of the exposure is toinsolubilize the polymeric coating adjacent to the support in the regionof the exposure.

The exposed elements are then developed in an organic solvent solutionin order to remove the unexposed area. This development can be carriedout with a mixture of 10 perecent benzaldehyde in methyl ethyl ketonefor 1 /2 minutes followed by rinsing in a fresh solution of the mixedsolvents. The result is to obtain three elements as shown in Fig. 2 ofthe drawings, each carrying a relief.

Solvents (cc.) and dyes (gm.)

Magenta Bath Yellow Cyan A Bath 33 Bath C Xylene Furiural Benzaldehyde"Dye A Dye B Dye O Azomethlne dye from Z-cyanoacetylcoumarone coupledwith 2-amino-fi-dlethylaminotoluene.

*Azomethine dye from wbenzoylacetani1ide coupled withN,N'diethyl-p-phenylenedlamine.

Azomethiue dye from l-hydroxy-Z-[B-(4'-acetamido)phenethyllnaphthamlde(Example 2, 8. Patent 2,589,004)

As is apparent; baths A, B- and C are used for dyeing the images 22, 12and 32 respectively and following this step each element is rinsed in asuitable solvent in which the dye has little if any soltiliility, forexample, mnexaasr following the magenta bath A, isopropanol followingbath B. and one of the Xylenes followingbath" C;

The d'y'e'delements new appear as shown in- Fig; 3 of the drawingswherein the elements having supports 10'; 2t and 30 are shown; ascarrying the yellow, magenta and cyan dyed reliefs 1 3, 23 and 33respectively.

ease the three relief images" on their separate supports are to beutilized as proofs for color printing plates or for simply" viewing asfull color reproductions, they are superimposed as sndwnin Fig. 4'- ofthe drawings,- and viewed by transmitted light. If desirable, theelements may instead be superimposed on a White background for viewingbyreflection; It Will be apparent that since the coloringmaterialine'ach' of the'relief images is locked into a moisture-impermeableresinous relief image, the dyes therein are appreciably more stableunder adverse conditions of temperature and humidity known to gfaduallydeteriorate dyes,than;are dye images in prior moisture susceptibleelements such as mentioned.

EXAMPLE- 2 In a manner similar to Example 1, subtractively colored dyeimages are prepared on sheets of cellophane to effect coloring of atleast the exposed regions of the elemerits before superimposition. I-ndoing so, if the commercial product is used usually consisting ofviscose coated with various substances, it is advisable in order toobtain utmost adherence of the relief images to the support, to" removeany solvent-soluble coatings on the surface of the sheet with solventsuch as a mixture of ethyl-- ene"dich1o1ide' and ethyl acetate followedby a Wash with methyl cellosolve acetate. Three such sheets are thencoated with the following" compositions:

ethyl ketone for 3 minutes follqwedj by a rinse in the] same solvent for1172; minutes and a short" rinse in riiethyl cenbs'ol've acetate.Afterthis; each sheet'i's dyed in' a: solvent solution of the approriate subtractivly colored dye correspondingto' th'e'i c'olor separationa's'peot each represents, such as thefollovvin'gz' Suitable cyan,magenta and yellow dyes foruse' in this dye solution are'yellow dyessuch a's'the a'zo' dye obtained by coupling o-nitro-p-chloroaniline with5';5-dime'thyl- 1,3-cyclohexadione awarding": to EXainple-4 and claim 7of MeNally-et al.- U. S; Patent 2,183,997, December 19, 1939; a magentadye suchas the azo dye obtained by coupling 2-chlbro-4-nitroaniline withbis-(fi-hydroxy; ethyl) sniliae'asdes'cnbed in Geigy Swiss Patent169,946, June 15, I934, and a blue or cyan colored dye such as the azodye obtained by coupling 2-amino-3,5-dinitrobenzenesulfonethylamide withl-Bp dihydroxy propyl- 2,7" climethyltetrahydroquinoline as described inthe Dickey et all U. S. Patent 2,391'-,886,'January 1, 1946.

After dyeing the reliefimages with the respective dye solutions they canbe rinsed with n-he'X-yl alcohol} dried and superimposed in the desiredmannerto yield full color: repraduetionsfef' viwiiig for the desiredpurposes m'e'ntionellpreviously.-

4 Other transparent supports upon which the light-sensitive compositionsmay be coated and upon which the colored relief images may be formedare, for example, films of polyvinyl chloride; polyacrylonitrile,polyamides, phenolic resins and the like as will occur to those skilledin the art. r

EXAMPLE 3 The dyed paiymeric' relief images can more advantageously beformed froiii predyed light-sensitive polymeric compositions 's'iicl'iasthe fonawing:

The dyes particularly suitable for use is thldye sannan s' above for"yein the" palymerie a r nals are the Swanson-ale dyesf as opifised tooil-soluble sr' watersoluble d es, dr' mixtures" of dyes, such as Thefirst three dyes enumerated are respectiyely substantially identical totanni ri lakes of Victoria Blue B, Auramine 0 c. I. 655 Victoria GrenlC,I. 657 Rotalin Redcortes'pondsto a riiixture of Rhodamine 6 SDN I. 752)and-Ant nna O (C. I. 6 55), the remaining- (lyes also jbeihg tannin lakes: 7

It is" thefefore apparent that basic dyes per se andpar'ticularlyt'afinln and similar lakes thereof are especially usefulfor dyeing the light-sensitive coating compositions.

Another group of spirit s'olub le" d yes of equal value in this processare salts of acid dyes such as the following? v I q Linn Fast Black PS;Luxol- Fast Blue MBS Lllilbl East Red BB Liner Fast Yellow T These dyesare arylguanidine' salts of acid dyes.

These dys pai tieula'rly Ro't'zilindyes are" prefe'i'ie since" theyarenetappreciably semenin the solvent develop'ensnlsedfor developing:the polynicrier'elief images such as t'r ichl-oroethylene' 01*" 20%methyl Cellosolvc acetate -in JiyleneI The dye compositions are coatedfor exain'plc 'orl' sheets of surface-hydrolyzed celluloseacetate,gelatin, subbed cellulose esters or on polyvinyl chloride. The sheetsare then exposed to continuous toned negatives as abovementiefieebyeapesurerareagu thest'lppo'lft, for example, tnemagm'a-celbredsheet re'eeiving' l irmint'lt'es exposure,

the cyan 1% minutes and the yellow 2. minutes at 4 feet from a35,-ampere carbon arc,.when empl'oyingf theiLuxol dyes. Diiferentexposure times up to minutesare required depending upon the'dyes'used;The exposedfilms are then developed with solvent vapor such as.trichloroethylene for about 20 seconds or ina tray of solvent such as20% methyl Cellosolve acetate in xylene for up to 5 minutes to removethe dyed polymer'in the areas not insolubilized by exposure to thecontinuous, tone negative. When the three single colored transparenciesare superimposed, a full color transparency of good quality is obtained.

EXAMPLE 4 When it is desired to;obtain a black-and-White monochromerelief image or to add a. fourth color to a 3- color printor'transparency inthe form of a black resin image, suitable images areprepared by coating a black light-sensitive composition such as thefollowing. onto a suitable support such as surface hydrolyzed celluloseacetate.

Polyvinyl cinnarnaten g'ram 7.5 Furfural cc 78 Xylene cc 30 Black dyegrams 0.75 4-,4-tetramethyldiaminodiphenyl ketonedo .75

A suitable black dye for this composition is a spiritsoluble dye suchas. Spirit Nigrosine (C. I. 864). As previously mentioned, dyes ofthistype are especially suitable since they are. retained bylth'e polymericrelief images during the development step. As in the previous examples,the sensitive coating is exposed. through the base in contact with acontinuous tonephotographic negative for 2 to 5 minutes at a distance of4feet from a 3'5-arnpere carbon arc. The image is developed for 2 /2minutes in a percent solution of furfurali in xylene or for up to 5minutes in the tray developer of Example 3' and rinsed for 30 seconds ina fresh mixture of the same solvents. The dye is insoluble in thisdeveloping solution andtherefore does not bleed out into the solvents.There results a clean, black, continuous tone'image reproducing adensity scale of approximately 1.5 in the negative. ln'an alternativemethod, the relief image is developed by immersing the exposed sheet invapor of trichloroethylene. The unexposed portion of the polymerdissolves in the condensate carrying'the dye'with' it physically whilethe dye insoluble in the trichloroethylene is'retained by the insolubleexposed polymer to produce a neutral continuous tone transparentpositive image.

EXAMPLE 5 Our process can be applied particularly to proofing colorprinting plates as follows: on three separate sheets ofsurface-hydrolyzed cellulose acetate, coatings are made with three predyed polyvinyl cinnamate solutions of the same composition as given inExample 3 above. Each sheet is then exposed for from 1% m8 minutes(depend ing on the dye used) at 4 feet from a 35-arnpere carbon arethrough a 266-line (or other appropriate ruling) halftone colorseparation negative corresponding to the color of the coating in vacuumcontact with the surface of the polymer. The exposed sheets are thendeveloped separately in a tray of 10 percent furfural in xylene for 2minutes or in 20% methyl Cellosolve acetate in xylene for up to 5minutes and rinsed for about 30' seconds in fresh solvent mixture. Afterdrying the solvents from the polymeric reliefs, they are superimposed toproduce a tricolor halftone color proof; With the proper selection ofdyes, dye concentration, and exposure, reproducible color proofs can bemade which accurately predict the out come of the final press sheet.

From the abovedescription it'will be apparent that since thelight-sensitive polymeric materials are highly stable, colorless orprecoloredlight-sensitive polymeric coated sheets in different colorscan be supplied t0-the trade for quickly making color proofs. Suchproducts conveniently include stripping films-having temporary supportsfrom which the solvent developedcoloredrelief images on thin transparentsupports'can-b'e stripped for superimposing to form a full'col'o'rreproduction. Also the relatively high light-sensitivity of thepolymeric materials used in our invention promises extensive commercialutility for the light-sensitiveproductsfor exposure directly in a camerafor the production of continuous'a'nd halftone multicolor images. Theprior art processesfor making colored reproductions by superimposingcolored relief images obviously suifered'in part due-to the low speed ofthe polymeric materials used'as'wellas the' p'oor resistance of suchmaterials to moisture;

In large scale production, for example, involving mechanical methods forlaminating'the above" individually colored transparencies together, ourprocess provides an intrinsically cheaper method thanobtainin'g'colorr'eproductions by means of integral .tn'pack colortransparencies based upon silver halides and color development methods.Thus, while the particular source of the color separation aspects usedinexposing the light-sensitive polymer coatings is not critical,negatives, for example, obtained by exposure of well known three-layerstripping' 'films having differentlysensitized silver halide emulsions;or negatives exposed in three-color one-shot cameras, are well suitedfor use in ourprocess;

The light-sensitive polymers given for illustration-in the aboveexamples are by no means exhaustive of those contemplated for use in ourinvention. Other polymers represented by that of Example 1, thepreparation of which are disclosed in-the. mentioned. Unruh et al.invention and in the. Unruh. et a1. U. S. patent application Serial No.246,517, filed September 13, 1951, now U. S. Patent 2,706,725, grantedMay 19, 1955, are the organic solvent-soluble light-sensitive materialscontaining polymeric units having the group in which R is a mononuclearor a polynuclear aromatic group particularly of the benzene and"naphthalene series in which the nuclei are substituted or not,particularly the polymers made by substantially completelyacetylating astyrene polymer and condensing with an aromatic aldehyde, or a vinylacetophenone polymer condensed with an aromatic aldehyde. These polymerscontain monomeric units having the general structure in which n isanumber fro-m 1 to 4 and Q is a mononuclear or polynuclear aromatic groupparticularly of the benzene or naphthalene series substituted or not andD is a single bond or aryl group of the benzene or naphthalene series.Accordingly, other polymers useful in our invention contain combinedpolymeric units of the following:

Isopropylbenzal acetylstyrene p-Hydroxybenzal acetylstyrenep-Dimethylamino acetylstyrene o-Chlorobenzal acetylstyrenep-Acetamidobenzal acetylstyrene p-Sulfobenzal acetylstyrene Anisalacetylstyrene Veratral acetylstryrene Anisal acetyl-o-methoxystyrenep-Hydroxybenzal acetyl-o-methoxystyrene o-Chlorobenzalacetyl-o-chlorostyrene p-Chlorobenzal acetyl-Z,S-dimethylstyrene 7Anisal acetyl-p-phenoxystyrene Anisal acetyl-p-bromostyrene Tolualacetyl-3,4-dimethoxystyrene Anisal acetyl-o-fluorostyrene ot-naphthalacetylstyrene Anisal benzal-acetylstyrene Anisalvinylmethyl ketoneBenzal acetylestyrene Benzal acetyl-o-methoxystyrene Benzal acetyl-o-,m-, p-chlorostyrenes Benzal acetyl-o-, rn-, p-bromostyrenes Benzalacetyl-p-beuzylstyrene Benzal acetyl-p-phenoxystyrene Benzalacetyl-3,4-dichlorostyrene Benzal acetyl-2,S-dimethylstyrene Benzalacetyl-m-methylstyrene Benzal acetyl-m-tert. butylstyrene Benzalacetyl-3,4-dihydroxystyrene The preferred light-sensitive materials arepolymers of vinylacetophenones condensed with a suitable aromaticaldehyde such as anisaldehyde.

Other suitable light-sensitive polymers are the cinnamalviuylacetophenone polymers disclosed by the Unruh et a1. applicationSerial No. 246,515, filed September 13, 1951, now U. S. Patent2,716,102. These polymers contain monomeric units having the generalformula wherein D represents a single bond or a mononuclear arylenegroup, Q represents a mononuclear aryl group, n represents a wholenumber from 1 to 4, and R is alkyl, preferably of 1 to 4 carbon atoms,and are obtained by condensing a cinnamic aldehyde with, for example, apolymer of a vinyl acetophenone compound; for example:

Polycinnamalacetylstyrene Poly-a-n-amylcinnamalacetylstyrenePoly-p-chlorocinnamalacetylstyrene Poly-m-nitrocinnamalacetylstyrenePoly-o-chlorocinnamalacetylstyrene Poly-p-methoxycinnamalacetylstyrenePoly-p-methylcinnamalacetylstyrenePoly-p-chlorocinnamalacetyl-o-methoxystyrenePoly-p-methylcinnamalacetyl-o-chlorostyrenePolybenzalcinnamalacetylstyrene Polycinnamalmethylvinylketone Thepolymeric material polyvinyl cinnamate used in Example 4 was prepared bythe methods of the Minsk et al. U. S. patent application Serial No.207,052, filed January 20, 1951, and is the substantially fully acylatedcinnamic acid ester of polyvinyl alcohol. While the substantially fullyesterified cinnamic acid esters of polyvinyl alcohol defined in theMinsk et a1. invention are preferred for use in our invention since theyare least moisture-susceptible, those cinnamic acid esters containing atleast 60 mole percent of any cinuamoyl ester groups are useful in ourinvention in the predyed or colorless light-sensitive elements of theforegoing examples. Cinnamic acid esters of other materials such as ofstarch and hydroxy alkylated cellulose (Minsk et a1. U. S. patentapplication Serial No. 308,284, filed September 6, 1952, now abandoned)can also be used to good advantage. It will also be apparent that wecanuse in the light-sensitive elements, mixtures of two or more of thelight-sensitive polymers and each of the three or more elements used inmaking full-color reproductions may comprise a different light-sensitivepolymer. As will also be apparent to'those skilled in the art, usefulresults can be obtained when the three light-sensitive polymericelements are suitably sensitized and are exposed through suitablefilters directly to the colored scene or subject to be reproduced, forexample, by use of tricolor filter exposures in a camera to obtain line,halftone or continuous tone reproductions. Optical sensitization of thecompositions is aided by use of the thiazole sensitizers disclosed inthe West and Robertson U. S. patent application Serial No. 314,806,filed October 15, 1952 now U. S. Patent 2,732,301.

In Examples 3 and 4 are illustrated the use of sensitizing agents forthe polymeric materials, for example, 4,4-tetramethyldiaminodiphenylketone. Other sensitizing agents useful in conjunction with any of theabove enumerated sensitive polymers are the nitro, triphenylmethane,anthrone, quinone, diphenylketone and thiazole sensitizers respectivelyof the Minsk et a]. U. S. patent application Serial No. 148,684, filedMarch 9, 1950, now U. S. Patent 2,610,120, granted November 7, 1950, theMinsk et al. U. S. patent application Serial Nos. 207,048-51, filedJanuary 20, 1951, now U. S. Patents 2,690,966, 2,670,285-7, and theabove West et al. invention. Typical sensitizing agents of thoseinventions are 2,4,6-trinitroaniline, Crystal Violet dye,2-keto-3-methyl- 1,3-diazabenzanthrone and 1,2-benzanthraquinone. Thepreferred sensitizer for all of the above uses where sensitizers aredesired is 2-benzoylmethylene-l-methyl-flnaphthothiazoline because ofits superior sensitizer activity and stability in combination with thepolymer coatmgs.

From the above description it will be apparent that we have providedmeans for preparing colored relief images on transparent supports forsuperimposing. Our invention is further adapted to preparing suchcolored polymeric relief or resist images upon metallic supports such asare useful in the printing trade. That is, in the preparation of resistsupon metal plates in photoengraving and photolithography it is desirableto provide a means for visual examination of the resist image beforeetching or proofing the plate. Consequently, when using thelightsensitive organic solvent soluble polymers such as indicated abovefor forming resist images, it is desirable to either bathe the resist indye solution or to incorporate coloring material into thelight-sensitive polymer composition before formation of the resistimage. The latter procedure is preferred partly since the after-dyeingstep can be dispensed with. However, prior to our invention dyes havenot been found which would not bleed from the resist images during thecourse of the solvent development step such as employed in Example 3.Now by use of the dyes, such as given above, in the initiallight-sensitive polymer compositions a variety of solvents such as thosegiven in Example 3 can be utilized for solvent development of a resistimage on various metal plates. Accordingly, in the preparation of a zinclithographic plate a composition such as set forth in Example 3 can becoated on a freshly counter-etched zinc plate, exposed to a suitableline or half-tone subject and developed in a solvent such astrichloroethylene in liquid or vapor form to obtain a well definedcolored resist on the zinc surface. In a similar manner the otherlight-sensitive polymers can be sensitized with the indicatedsensitizing agents, and resists formed on zinc, magnesium or other metalplates. In a similar manner colored polymeric images can be formed onother surfaces such as ceramic ware, glass, paper, plastic, etc. forpurely decorative purposes.

, What we claim is:

A method for preparing a colored photographic reproduction whichcomprises exposing to separate color aspects of a subject at least twophotographic elements each carrying on a transparent support a layer ofa lightsensitive organic solvent-soluble polyvinyl cinnamatesubtractively colored with a spirit soluble dye, to insolubilize 10 theexposed areas of the layer, removing only the soluble References Citedin the file of this patent areas of the exposed layers with an organicsolvent in UNITED STATES PATENTS which said dye is insoluble to obtainsubtractively colored relief images of insoluble polymer on each supportcorg z i responding to said color aspects, and superimposing the 5 p.amec e resultinn elements 2,610,120 Minsk et a1 Sept. 9, 1952 FOREIGNPATENTS 384,364 Great Britain Dec. 8, 1932

